As generations of processors and other integrated circuit devices have built upon previous generations, the numbers of pins required have generally increased. Even when pins are no longer used they are typically retained for backwards compatibility purposes. However, this may increase the cost and complexity of successive generations.
For example, increased pin count increases the size of an integrated circuit, which may increase manufacturing costs. Routing of signals, both within the integrated circuit and on the host circuit board, may increase in complexity as the result of increased pin count, which may increase cost and/or design time. Other disadvantages may include timing and signal integrity problems, power plane and termination complexities and voltage incompatibilities.